1. Field of the Invention
This invention relates to the grinding of solid material and, more particularly, to the grinding of municipal solid waste for either disposal or further processing.
2. Description of the Prior Art
Various apparatus and methods are employed today to shred municipal waste for disposal or further processing. In some of these systems conventional ball or rod mills having lengths greater than their diameters are used. However, in the systems, it has been found that it is very difficult to move the shredded waste horizontally through the mill because of the low bulk weight. This often results in mill overload which requires shut-down and cleaning of the material from the mill. The difficulty also has resulted in an energy loss because shredded material in traveling the required horizontal distances is continually ground finer.
In some operations to shred municipal waste, hammermill type shredders are employed. However, if a hammermill is used, the impact velocities must be low to minimize the detonation hazard associated with some items often found in municipal waste. In many cases the impact velocities are so low the mill is not an effective shredder. Also, the maintenance costs associated with hammermill shredders are relatively high when compared to tumbling mill shredders.
Accordingly, the objects of the present invention include a method for grinding municipal waste wherein the material is shredded in an economic, safe and efficient manner.